Radiotherapy equipment for treating a patient by irradiating his or her affected part with therapeutic radiation is known.
In radiotherapy, it is desirable that radiation treatment using therapeutic radiation on an affected part be accurately performed to reduce a dose radiated to normal cells around the affected part and reduce any influence on the normal cells.
Here, because a position of the affected part (specific portion) varies with the passage of time due to a subject's respiration or the like, it is also necessary to vary an irradiation position of radiation therewith and perform tracking irradiation. Thus, technology for embedding a marker inside the subject, pre-measuring relative positions of the marker and the affected part using a computed tomography (CT) image or the like, and estimating a position of the affected part from relative positions to positions of a plurality of markers after a predetermined time has been proposed (for example, see Patent Literature 1).